Lobster Truffle Pot Pie

Name: Lobster Truffle Pot Pie
Ingredients: 2 lemons, halved; Kosher salt and freshly ground black pepper; Five 1 1/2 to 2-pound lobsters, tails and claws separated from the body, heads and bodies reserved; 5 tablespoons unsalted butter; 5 carrots, two cut into large dice, three cut into medium dice; 4 yellow onions, two cut into large dice, two cut into medium dice; 2 stalks celery, one cut into large dice, one cut into medium dice; 1 bay leaf; 3 cups heavy cream; 3 cups milk; 2 russet potatoes, cut into medium dice; 1 black truffle; 1 cup peas; 2 tablespoons finely chopped fresh flat-leaf parsley; Freshly grated nutmeg; 1 sheet frozen puff pastry, thawed; 1 egg, beaten with 1 tablespoon water